Current typical vehicle speed control systems utilize dashboard/steering wheel controls to regulate the speed of a vehicle at a level set by the driver without the driver having to maintain pressure on the accelerator pedal. The driver brings the car up to a desired speed and turns on the cruise control. Next, the driver programs that speed into the system by pressing a button. A sensor measures the speed at which the vehicle is traveling. Based on the difference, if any, between the actual speed of the vehicle and the desired speed set by the driver, a control logic controls a servo motor to set the throttle so that the speed of the engine is at the level needed to have the car travel at the desired speed. This type of cruise control, however, is difficult to use in traffic since frequent changes in the desired speed are required.
In order to accommodate the driver's typical behavior in traffic, cruise control systems have been developed that control the speed of the vehicle based on a position of the accelerator pedal. For example, one known prior art control system disclosed in U.S. Pat. No. 4,615,409 provides a snap-in detention device at the junction point of an acceleration section and a deceleration section such that a foot can rest with a force slightly above the weight of the foot against the accelerator pedal while the speed of the motor vehicle is maintained constant. However, for low vehicle speeds (i.e., deceleration or starting from a stop position), the driver is required to push the accelerator pedal to a predefined "0" position to get the vehicle moving.
Another known prior art speed control system that utilizes the position of the accelerator pedal to maintain the speed of the vehicle is disclosed in U.S. Pat. No. 4,541,052. In this system, the speed of the vehicle is controlled based on whether the accelerator pedal is an a transient operation mode or in a steady state operation mode. When steady state s indicated, the vehicle power output is brought into correspondence with a power command determined according to the difference between the vehicle velocity and a remembered velocity. This system, however, describes a linear relationship between output power and accelerator position which does not result in a normal feel for a driver used to existing vehicles which have a nonlinear relationship that varies with engine speed.